The β3-adrenergic receptor (B3AR) plays a major part in lypolysis in white adipose cells and heat generation in brown adipose cells. The existence of the mutation replacing tryptophan at position 64 in the amino acid sequence of B3AR with arginine (Trp64Arg) is said to reduce the resting metabolic rate by 200 kcal, and to be involved in obesity with abdominal fat and in insulin resistance.
If the mutation resulting in the Trp64Arg mutation in B3AR (also referred to as “B3AR Trp64Arg mutation”) exists, a recognition site of a restriction enzyme emerges at the position of the mutation. Therefore, the mutation can be detected by a method of amplifying DNA by PCR so that a portion including the mutation position should be amplified, digesting the amplification product with a restriction enzyme and determining whether the DNA has been digested or not by electrophoresis (PCR-RFLP) (for example, refer to The Japanese Journal of Clinical Pathology, vol. 44, 8, pp. 778-782, 1996).
Because PCR amplifies templates of several molecules several billion times, even a trace amount of contaminant may cause a false positive or false negative result. In PCR-RFLP, the amplification product needs to be collected and subjected to a treatment with a restriction enzyme after PCR, and therefore the amplification product may contaminate the subsequent reaction system. Accordingly, a false positive or false negative result may be obtained.
Further, DNA is treated with a restriction enzyme and then subjected to electrophoresis after completion of PCR. Therefore, time required for the detection becomes extremely long. In addition, because the procedure is complicated, automatization is difficult.
Furthermore, a method is generally known in which a region containing a mutation is amplified by PCR, then a melting curve analysis is performed by using a nucleic acid probe labeled with a fluorescent dye, and the mutation is analyzed on the basis of the result of the melting curve analysis (Clinical Chemistry, vol. 46, 5, pp. 631-635, 2000; Japanese Patent Application Laid-open (Kokai) No. 2002-119291).